Design of nickel cobalt molybdate regulated by boronizing for high-performance supercapacitor applications

Nickel-cobalt-based molybdates have been intensively investigated because of their high theoretical specific capacitance and multifarious oxidation states. Here, we have successfully synthesized hierarchical structures (Ni₃B/Ni(BO₂)₂@Ni_xCo_yMoO₄) by boronizing Ni_xCo_yMoO₄ nanosheets on flexible carbon cloth substrates. Benefitting from the synergistic effect among Ni₃B, Ni(BO₂)₂ and Ni_xCo_yMoO₄ in hybrid architectures, the electrode material possesses higher capacity of 394.7 mA h g^-1 at 1 A g^-1 and a good rate performance (309.5 mA h g^-1 maintained at 20 A g^-1). Then, a hybrid supercapacitor assembled with Ni₃B/Ni(BO₂)₂@Ni_xCo_yMoO₄ and activated carbon as the positive and the negative electrode, displays a high specific capacitance of 370.7 F g^-1 at 1 A g^-1 (210 F g^-1 at 10 A g^-1), a high voltage of 1.7 V, and a high energy density of 131.8 W h kg^-1 at the power density of 800 W kg^-1 (still 74.7 W h kg^-1 maintained at 8000 W kg^-1). This study widens the research scope of boronizing pseudocapacitance materials and reveals a high application potential of Ni₃B/Ni(BO₂)₂@Ni_xCo_yMoO₄ for energy storage devices in the future.